He is not your average Hollywood star - but his film has become one of the most successful in American history, and is set to match that success in the rest of the world.

He is green, huge, ugly and bad-tempered - but loveable, with no movie-star ego or the wage demands that go with it.

And he does not exist - apart from inside the computers of film studio DreamWorks.

Cameron Diaz gave her voice to Princess Fiona

His name is Shrek and he is the product of the most revolutionary animated film techniques around, taking 200-300 people two years to bring to life.

His film - named after him - is set to become one of the most popular animated features ever, fast catching up other animated epics The Lion King and Toy Story 2 in the all-time box office stakes.

Living in a land beset by fairy-tale characters, Shrek is an ogre whose story reminds audiences that beauty is only skin deep.

His Scottish accent is supplied by Mike Myers while Cameron Diaz and Eddie Murphy's provide the voices for Princess Fiona and Donkey.

But the people behind the animation are bigger stars in their field.

Jeffrey Katzenberg set DreamWorks up with Steven Spielberg and David Geffen in 1994, and the trio have already had live-action hits with American Beauty, Gladiator and Saving Private Ryan.

Jeffrey Katzenberg: Has already ordered a sequel

And they are now said to be worrying Disney with their animation output.

Katzenberg says he chose to make Shrek, which was originally a children's book by William Steig, because it is a "funny irreverent, subversive way of telling a big-hearted story".

"In that book was this great little kernel of an idea. Instead of prince charming as the hero of the movie, [it is] a big, green, stinky ogre who journeys out into the world," he told BBC News Online.

Shrek is only the fifth big screen release made using the latest computerised techniques, known as Computer Generated (CG) imaging - which means the characters are not drawn first, but created and brought to life within the computer.

"It's revolutionary in terms of technically what it's done because it's such a huge quantum leap over what was being done literally only a year or two ago," Katzenberg says.

Princess Fiona during stages of development

But while it may be at the cutting edge now, he is under no illusions that they, or someone else, will overtake it soon.

"A year or two from now, it will look obsolete because that's how amazing and how fast things are changing in terms of computer animation."

It is the first time film-makers have created realistic human characters using CG techniques - and also the first time they have had to build a range of different settings, including caves, lava, forests and castles.

For humans, like Princess Fiona, voiced by Diaz, animators created the skeleton in the computer before adding muscles, telling the computer how they behave, and finally adding the skin.

"There's a big difference between what you expect from an ant's facial expression and a princess's facial expression," co-director Andrew Adamson says.

But the animators sometimes did their job too well and made her look too realistic for the style of an "animated story book", he says.

Shrek was Jenson and Adamson's directorial debuts

"At some points she... looked a bit like this creepy mannequin, and at other points she looked a bit too real and didn't really fit in the scene where she had to talk with the donkey."

Some techniques did not even exist when they started work - meaning New Zealand-born Adamson had to hope somebody would invent a particular animation method by the time they needed to use it.

"In the end, it's not just a fun movie," she says. "There's a message there that's worth saying about not judging people by what they look like and not letting other peoples' expectations rule your life."

The public and studio have liked Shrek so much that Katzenberg has already ordered a sequel.

A script has been written, but all Katzenberg will reveal is that "ogres are not made to be kings and queens".

"We had so much fun working with the characters and the actors of this movie... that we're not ready to retire them yet."